Aesica was built after AD 127 and was, together with Carrawburgh, one of the last of the primary forts to be built (with the exception of Newcastle which came much later). The fort faced east and was 3 ½ acres in size. The fort is close to the broad wall foundations of Hadrian’s Wall and the north wall and rampart lie above milecastle 43. Aesica was built in stone and had a bath house 100 yards to the south. By the wall close to the north-east angle tower there was a smithy and outside the fort were a series of 4 defensive ditches across which, to the south, ran a road connecting the fort to the Stanegate. The fort was supplied with water from the Caw Burn via an aqueduct which stretched for 5 miles north of the fort.

There were six periods of construction at the fort.

1 The west gateway was initially built under Hadrian in 128 or shortly afterwards.
2 There was building work under Marcus Aurelius

3 The gateway was reconstructed under Severus, The east gateway shows a date of 205-11 (RIB1736)

4 A granary was built in 225 under Alexander Severus

5 The walling-up of the southern half of the west gate took place under Diocletian whilst Constantius Chlorus was in Britain. (296-306)

6 The west gateway was completely blocked under Theodosius in AD368.

The first garrison listed at Aesica is an infantry unit, Cohors VI Nerviorum Quingenaria Peditata.

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